dickieson



Feb. 14, 1956 E. F. DlcKlEsoN, .1R 2,734,346

r APPARATUS FOR CONTROLLING REFRIGERATING SYSTEMS Filed Feb. 4, 1949 3Sheets-Sheet l Feb 14, 1956 E. F. DlcKlEsoN, JR 2734,346

APPARATUS FOR CONTROLLING REFRIGERATING SYSTEMS Feb. 14, 1956 E. F.DlcKxEsoN, .1R 2,734,346

APPARATUS FOR CONTROLLING REFRIGERATING SYSTEMS Filed Feb. 4, 1949 3Sheets-Shee1'l 5 United States Patent APPARATUS FOR CONTROLLING-REFRIGERATING SYSTEMS Edward F. Dickiesoln Jr., Detroit, Mich.;Nathalie L. Dckieson, executrix of said Edward F. Bickieson, Jr.,deceased, assignor to Nathalie L. Dckieson v Application February 4,1949, serial Np. 14,585

7 claims. (ci. 62-4) This invention relates generally to refrigerationand more particularly to a method of and apparatus for the control of arefrigerating system whereby the condensing unit thereof is preventedfrom becoming overloaded.

An object of this invention is to provide an improved method foroperating a refrigerating system. ff Another object of this invention isto provide a new controlling means for controlling the flow of vapor toa-compresson f A` further object of this invention is to provide such amechanism with means responsive to the suction pressure of thecompressor. Y g

A further object of this invention is to provide such a means which isresponsive to discharge pressure of the compressor.

A'further object of this invention is to provide a novel control systemhaving the aforesaid characteristics and the control of which isadditionally-modied inaccordance with conditions contained with thespace to be re'- frigerated. t t

Other objects will be apparent from the specification, the claimsappended thereto and the drawings in which drawings Figure 1 is adiagrammatic view of a refrigerating system embodying the invention;

Fig. 2 is a view in partial central vertical section of a controlelement embodying the invention which may be utilized in the system ofFig. l, the device being connected between the outlet of the evaporatorand the inlet of the compressor;

Fig.' 3 is a view in central vertical section of a fied form of thecontrol element shown in Fig. 2;

Fig. 4 is a schematic view of a refrigerating system embodying amodified form of the invention; g

Fig. 5 is a view similar to Fig. 3 showingthe manner in which theapparatusv of Fig. 3 may be modified to accommodate itself for use inthe refrigerating system shown in Fig. 4;

Fig. 6 is a view in central vertical section of a control mechanism usedin the system of Fig. 4 the device being connected between the receiverand the compressor inlet and in open communication with the evaporator;

Fig. 7 is a diagrammatic view of a still further modied form ofrefrigerating systems embodying the invention; and

Fig. 8 is a View in central vertical section of a control element foractuating the throttle of a governor-controlled gasoline engine in thesystem of Fig. 7, the control element of this figure being employed tovary the setting ofthe governor over al definite range of engine speeds,the control device of Fig. 6 being used to further vary the compressorcapacity when necessary in accordance with the demands of the spacerefrigerated. A

Referring to the drawings by characters of reference, 1 indicatesgenerally a compressor having its discharge outlet connected by means ofa conduit 2 to a condenser 3 wherein the gaseous` refrigerant pumped bythe compressor 1 is condensedto a liquid in the usual manner.

modi- 2,734,346 Patented Feb. 14, 1956 A receiver tank 4 receives thecondensed liquid from the condenser 3. Liquid refrigerant ows from thetank 4 through a conduit 6 under control of a thermostatic expansionvalve 8 to an evaporator 10 located within a space 12 which is to becooled. The evaporator 10 is connected by means of a suitable conduit 14`to the inlet 16, Fig. 2, of an overload controlling mechanism genrallydesignated 18. The outlet 20, Fig. 2, of the mechanism `18 is `directlyconnected to the inlet port of the compressor 1. f A suitable source ofrotative energy such as the electric lmotor 22 may be connected as bymeans ofa belt 24 for driving the compressorl.

lThe motor 22 is controlled in a suitable manner such as athermostat'generally designatedl 26 and embodying an on-and-otf 4switch(not shown) for making and breaking currentin one or both of the linesL1 and L2. The thermostat 26 embodies a temperature sensitive elementy28 which is located within the space 12 to be cooled and operates inthe usual manner to close the switch contacts in the thermostat 26 uponincrease of temperature in the space 12 above'that desired and to openthe contacts in the thermostat 26 when the temperature in the space 12falls to a predetermined low limit. It will be vapparent `that ifdesired a control such as that shown in my copending application, SerialNo. 750,947 filed May 28, 1947,'now U. S. Patent No.2,626,506, forControl Mechanism, could be used to vary the rate of speed of the motor22` instead of merely turning it on `and off' whereby the temperaturewithin the refrigerated space might be maintained within predeterminedlimits. It will be obvious that a gasoline engine or othery source ofprime energy could be used to drive the compressor 1 and the operationof the engine be controlled by a suitable temperature responsive elementadapted for use with that particular source of prime energy. Such anelement and system is shown in my above-mentioned U. S. Patent No.2,626,506, and also in my U. S. Patent No. 2,626,507 for Method andApparatus for Controlling Refrigerating Systemsl The energy required todrive a compressor 1 will be a function of the weight of the uid beingtransferred by the compressor'per unit of time and also proportional tothe difference in pressure between which the uid is transferred. As iswell known in the refrigeration art, when the `temperature of theevaporator 10 is higher than normal, the refrigerant pressure thereinincreases and more power is required to drive the compressor. lf thedriving mechanism,.such as the motor 22, were selected so that therewould be suicient power to drive the cornpressor 1 at all pressureconditions imposed thereon then when the vcompressor 1 is operating withnormal pressures in the evaporator 10 andthe condenser 2, the motorwould be partially loaded and would not operate as efliciently as a morenearly fully loaded motor. Also the cost of the larger size motor wouldmake its use uneconomical. The control 18, placed in the suction line 14and in communication with the inlet port to the compressor 1, regulatesthe pressure at the compressor inlet and consequently the weight offluid being pumped by the compressor to prevent such weight-frombecoming excessive and morethan the motor 22 is capable of pumping.

The apparatus 18 comprises generally a housing member 30 having a uidflow passageway 32 leading from the inlet 16 and opening into the outlet20. In this passage is arranged a valve member 34 which may be of thebalance buttery type as shown pivoted upon a shaft l valve 34. That is,when thevalve 34 is in the position as shown, maximum lluid can owthrough the passageway 32 while when the valve has been rotatedclockwise from the position shown to a substantially closed position,the tlowof .iluid through .thepassageway =16is -substantially reduced if.not entirely stopped. lhe positioning of the valve 34 is vrdeterminedby Vtheresultantof the forces exerted by a piston .-38 sensitive ltodischargepressure and by the lipid force exerted on 1.a movableidisk 40within the pressure chamber 4 2. 'Iheiplessure 1vvithinwtlle chamber 42is lsubstantially .that -which appearsat -the end of `the passageway 32adjacent the outlet 20, such vpressure being communicated theretoYthrough an aperture 43 in the side wall of -the passageway .32 andsogpositioned that it will be ontheend of theipassageway .32adjacent theoutlet 20 and separated from theinlet 16 by means of the valve y34 asthe valve-moves-toward 'closed position.

The housing 3,0-is provided with -a hollowbossx44 extendingoutwardlyofthe Side wallof thspaSSgeway .32 coaxially of the yaperture `43andserves as .the outer peripheral wall o frvthe :chamber 4 2. The `innerwallsof the chamber -.42 -comprises Vthe peripheral surface of :abellows member 46. The member 46 fis'sealed atA one :end-to .an annularplate 4 8 Vwhich abuts l.the outerend wall ,of ,the boss 44 to form an.end Wall of Lthechamber 42. ,The member 46 is sealedv at its other-endto the disk 40 within the chamber 42 and` inwardly .of -the common wall:section 49 between vthe passageway 32 and the pressure .chamber 4 2. AYthrust rod 5 0 ispivotally isecuredatone .end.portion by the pin 52 4tothe butterflyvalve 34 and issecured at its other end to the disk40 Yasoy meansfof atscrew 51. One end portion of apiston r..o.d 54 is alsopivotally secured by .the pin 2to .the valve 34 and atl its `other endportion is made semi-spherical for reception in amating semi-sphericalaperture in the piston 38. The `piston 38 is snugly butslidablypositioned within a piston chamber 56 which yis located in la b oss.57extending-outwardly of the passageway 32, and .is preferably coaxialwith the chamber 42 and aperture 43. The portion ofthechamber56-.outwardly of the piston 38 is s uitably :arranged to :be connectedby means of conduit 58 to thedischargeconduit V2 whereby the dischargepressure of thefcompressor 1 acts upon the piston 38 to urge it inarghtward or inward direction (Fig. `2) in proportion to .the dischargepressureof the compressor.

The compressor suction .pressure is transmitted `through the aperture 43 into'the chamber l42fand acts `upon Lthe end member 40 of the :bellows.46 ;in .a .direction .to col.- lapse the bellows 0r move :the Wall 40'toward'.the right. In -this manner an Iincrease iineither or both the.suction and discharge pressure of 4the compressor 1"will exert a forcevtending to close the valve 34 .to reduce .the working load on fthecompressor. A spring-^62 .is located concentrically within thebellowsmember :46 .and is `arranged with its oppositeends abutting lthedisk A40 :and a transverse wall 64Irespectively. The .forcezexertedbythe spring will-.determine :the pressures necessary 'in lthe chambers5.6 and 42 .for positioning the valve :34 in its various controllingpositions. The #transverse wall vor plate member -64 forms the fixedwall of :the .expansiblecontractable chamber 6 5 formed 'within thebellowsmember 46 and is provided with afluid flow restrictingorifice 66extending therethrough. Ahollow cap :68 isrsecured to the -outersurfaceof theiplate member 64f-with its. hollow :interior or chamber 69, facingthe :memberl 64'. AI-he cap 68, plate members 64 and 48 are suitablyheld tightly together and to :the end -wall of ,the boss -44lin.fluidtight engagement by lmeans of cap screwsor other means (notshown).

The chamber 65 is completely filled and the chamber 69 partially filledfwith a uid such as oil. The .oil is;introducedl into. the chambersfGSand 6 9 vthrough an .intemally-threaded aperturef/'U in the cap :68=which,after .introduction of the oil, is closed as lby means lofyfa'p1ug""/'2, such lintroduction preferably ibeing made Awith the axisof the chamber 165Y extending in a vertical direction lwith the aperture70 uppermost. The plug 72 has a venting aperture 72a to permit the iluidlevel therein to vary while still being maintained :at atmosphericpressure. The member 64 is provided with a passageway 73 for venting ofthe chamber 65 during the introduction of the oil after which it isclosed by a plug 74. As the movable wall or disk 40 moves back andforth, the volume of the chamber 65 varies 'and the necessary oil`lows'through the orice 66, the restriction to How Athrough the orifice66 acting to damp the -movement vof the movable wall 40 and thebutterfly valve member 34 softhattheposition of the valve member 34 willbe substantially proportionate :to the average discharge .and suctionpressure .rather than to in stantaneous or transient pressures whichmight appear for various reasons and .also prevents a hunting action ofthe valve.

The position of the valve member 34, as shown in Fig. 2, is .that inlwhich :the compressor is .operating at or below its maximum ratedloading. Let us now assume that for some reasons, such as the placing.of an article yto'be refrigerated in thespace 12 the pressurewithintheevaporator 10.increases. This increase of pressure willnormally increase the pressure at the inlet of the compressor 'land agreater weight'of refrigerant gas will bepumped per unit of time by Ythe.compressor 1. This increase in Weight of the gas being pumped by thecompressor 1 .increases the power required to drive the compressor andalso tends to increase the discharge pressure .due to the fact that agreater differential in temperature must bemaintainedzbetweengthecondenser 3 and vthemedium to whichthe added heatis dissipated. `This increase in suction pressure passes through theaperture 43 and reacts upon the outer .face of themovable Iwall -40tending `to move the .wall to :the-right. Upon :the occurrence .of apredetermined combined value O fdischarge .and suction pressures whichmay be 1an increase in either .or both, the controlling mechanism 18will start to throttle the ow of suction vapor to .thecornpresserduetomovement of the .valvei34 towardclosedposition. This increase :inone .or both the discharge and suction pressures acts on the piston 56and the wall .40 tondiugfto urge them toward right to rotate the.valvel34 in a clockwise direction restricting the owof refrigerantvapor frorn'the evaporator 10 tothe compressor ,1. lThe relative,pressure :areas of the piston 56 and wall 40 .are chosen .itoprolduceneffect `corresponding to the relative changein :power .characteristicsof the compressor with change in suction and discharge pressure. Thespring 6 2 `is chosen to calibrate 'the 4mechanism 1-8 .to .the absolutemagnitude of pressure so that the .throttling :effect of the valvev 3 4vto control the .quantity of suction'gas admitted to the compressor willnot permit the compressor to receive `agreater -weight .of refrigerantvapor than that for :which the vmotor 22 is designed. As the evaporatorpressurefalls the .opposite effect will be .produced on the apparatus 18to reduce any restrictive .effect of thewalve 34.

In Fig. 3 there is .shown a -modiied form of .control apparatus 18a'which .acts to perform Va similar function as does the apparatus =18but is koperated :by servomotor 9.0 responsive to fthe intake -andexhaust pressures ofthe compressor -1. In this form, the intake orsuction pressure is applied directly to the chamber 118 while thedischarge or exhaust apressure of -the compressor 1 .isappliedftotheundersidc. of the'valve .13.4 Whichslides within tl 1,e.bushi-ng 92. Theupperportionpof the value 1'34 .isof larger diameterthanthe port 136 to provide an annular pressure -sensitivearea -againstwhich the .discharge i pressur e actst o .exert a force on vthe Awall130 proportional to the discharge pressure. The diameter .of the port136 may remain .constant while the outer Adiameter of thevalve1-34-and.inner diameter of the bushing 92 may be'-vari ed'to :providelthe correctarea of annula-r pressure sensitive 'area relative ltothe area of wall130 for'opcration off'the `valve -1'14 substantially as described inconnection'with-the operation of valve 34.

.5 The apparatus shown ineFig. 3 comprises a pair of hollow housingmembers 100 and 102. The housing member 100 is provided with an inletopening 104 adaptedgto be secured to thesuction conduit 14 or equivalentofa refrigerating system whereby the suction gases from the evaporatormay be introduced to the interior of the hollow housing member 100. Thehousing member 100 also has an outlet passageway 106 leading from thehollow interior thereof outwardly. of the housing member and is adaptedfor connection to the intake port of thecompressor 1. The housing member100 is also provided. with a piston chamber 108 in which a piston 110 ispositioned for movement. The piston 110 has a piston rod 11,2 at one endof which is carried a valve member 114 which is coactable with a valveseat 116 through which the suction vapors pass from the inlet 1.04 tothe hollow interior of the housing member 100.

` The interior of the housing member 102 is open to the hollow interiorof the member 100 through a hollow tubular member 122 which ispress-fitted or otherwise suitably sealed as by brazing to the bodymembers 100 and 102. A bellows member 124 is positioned within thechamber 118 and is secured at one end to an annular' ring 126-which Visclamped between a cap member 128 and the body member 102. The other orlower end of the bellows member 124 is closed by means of a movablewallor disl; 130 so that a pressure chamber 118 is formed ex'teriorlyVofthe bellows 124. The interior of the bellows 124isopento atmospherethrough bleed passageway 4131 in the cap member 128. A controllingmemberV such as needle valve 134 is actuated by the wall 130 and coactswith valve port 136 to control flow of high pressure refrigerant vaporfrom an inlet 138 to an outlet conduit V140 for providing the necessaryenergy to actuate the valve 114. Atubular member 141 is carried by thecap member 128 and serves as a stop to limit upward movementv of the endmember 130. The usual helical coil spring 142 is arranged interiorly ofand concentric with the bellows 124 and seats at one end against thecover member 128 and its other end against the inner surface of themovable wall 130. It will now be apparentv that the valve 134 will beactuated by change in pressure within the housing 100 to control theflow of actuating fluid to actuate the valve 114.

The piston rod 112 associated with the valve 114 is provided with aninternal bore 146 which fits over a guide member 148 carried by thehousing member 100 whereby the piston rod'1l2 and valve 114 will beguided for vertical movement. In order that there may be no fluid pocketwithin the bore 146 to interfere with free movement of the valve 114 inaccordance with change in pressure across the piston 110, the piston rod112 is provided with a venting passageway 150 opening outwardly throughthe piston rod 112 into the hollow interior of the housing 100. Thepiston 110 is provided with a controlled or restricted fluid ow port 152for a purpose which will be made clear presently.

Y It is believed that it will be obvious from the discussion of theoperation of theapparatus of Fig. 2 that as the suction pressure of thecompressor increases such increase in pressure will be transmittedthrough the passageway 120 formed by the hollow interior of the member,122 into the 'chamber 118. Such increase in pressure causes the movablewall 130 to move upwardly thereby moving the needle valve 134 upwardly.Likewise an increase in discharge pressure causes the valve 134 to exertan increased upward force on the wall 130 for moving the wall'upwardly.Such upward movement of the valve 134 permits an increase in fluid flowfrom the high pressure fluid source through the conduit 140 to theunderside of the piston 110. Such flow of iiuid through the conduit 140will increase the pressure in the chamber 154 proportionately to theamount of opening of the valve port `136. Y Such increase in pressure inthe chamber 154 causes the piston 110 to move upwardly thereby movingthe valve member 114 closer to the valve seat 116 for restricting iiowof tiuid from the evaporator 8 to the com'- pressor 1 so that thesuction pressure of the compressor, 1 does not rise beyond the desiredvalue. Conversely, as the suction pressure and/or discharge pressuredecreases, the pressure in the chamber 118, external of the bellows 124,decreases permitting the spring 144 to move the wall downwardly therebymoving the needle valve 134 closer to its seat 136 and lowering the flowof uid to the conduit to the chamber 154 thereby lowering the pressurein the chamber 154 permitting the valve member`114 to move downwardlyaway from the valve seat 116 for decreasing the restriction to uidv owthrough the casing 100. The flow capacity of the passageway 152 issuiciently small with respect to that of the port 136 so that a pressurediiferential of varying magnitude across the piston 110 will beestablished by the varying position of the valve 134.

The refrigerating apparatus of Fig. 4 is similar to that of Fig. l inthat it comprises a compressor 1, a condenser 3, a receiver 4, a liquidline 6, an expansion valve 8, an evaporater 10 located in the space 12which is to be refrigerated, a suction line or conduit 14 and adischarge conduit 2. In this form of the invention the motor 22 or othersource of prime mover is'continually energized whereby the compressor isoperated continually. The pumping capacity of the compressor however isvaried under the actuation of the control mechanism 200 (shown in Figs.4 and 6) and takes the place of the on-otf thermostat 26 used in thesystem of Fig. l. The mechanism 200 asY used in Fig. 4 is connected tosupply controlled amounts of high pressure refrigerant vapor from there,- ceiver 4 through the conduit 22,2 to the fluid chamber 154 of thecontrol mechanism 18a whereby the position of the valve member 114relative tov its seat 116 may be controlled as a function of the'pressure in the evaporator 10 to maintain a desired temperature in the.space 12. AIn this regard it will be noted that the control of themechanism 18a by the mechanism 200 will not interfere with the beforedescribed operation of the mechanism 18a by the control 90 to preventundue overloading of the driving motor 22 since the overload controllingfunction occurs at high evaporator pressures and the temperaturecontrolling function occurs at low evaporator pressures in which thismotor 22 has ample power to drive the compressor 1. ln the system ofFig. 4, there is provided a valve 114 actuated by two controllingdevices to perform an evaporator controlling'function at low evaporatortemperatures and pressures and a compressor controlling function at highcompressor power requirements to limit the compressor loading so thatthe power required'thereby does not exceed the power which may safely bedelivered by the motor 22.

The mechanism 200 is shown and claimed in my copending applicationSerial No. 74,586 iled February 4, 1949, now U. S. Patent 2,626,507.Essentially the ap.- paratus 200 comprises a pressure sensitivechamber202 communicatively connected by passageway 204 and conduit 206 to theevaporator 10 whereby the pressure in the chamber 202 is proportional tothat in the evaporator. The position of the movable wall 208 will be afunction of the pressure within the evaporator l0. The wall 208 moves acontrolling valve element 210 whereby tluid ilow past the valve seat 212is controlled as a fuction of evaporator pressure. High pressure iluidfrom the receiver 4 is conveyed by means of conduit 214 to the inlet 216of the apparatus 200 which is in open communication with one side of thevalve seat 212. Fluid passing through the seat 212 ows into the chamber218 which has an outlet 220 communicatively connected by means ofconduit 222, Fig. 5, to an inlet 224 opening into the chamber 154 andwhich was shown plugged in Fig. 3. When plugged, the mechanism 18a isadapted for use as above described in the system of Fig. l. When theinlet 224 is connected with conduit 222 as shown in Fig. 5, the

mechanism is suitedfor use in the system 'oiFig 4. A contr1`knob'226ofthe apparatus 200 is rotated' so `that 'the spring 228 will opposeupward movement ofthe 'movable wall'208 Asu'iciently so that the valvemember '21'0 wfill Zbe positioned relative Yto the valve jport 212 atthe iesired evaporator pressures to regulate the flow of the highLpressure uid to the chamber1'54 to cause the' valve mcmber`ll4,'Fig. 3,to be positioned relative to its seat 116 torestrict'ilow of 'uid fromthe evaporatorlt) to thecompressor l. 'This *position is such astopermit just'suf- Vticientfuid owfro'mthe evaporator 10 to the compressor1 to maintain the ldesiredpressure in the evaporator'10 irrespective ofthefact that the compressor lhasa tendency'to lower this pressure belowthe desired limit.

7' The control 20'0 may be.used .with or without the `overload`servomotor90 vvshown in ',Fig. 3. lf used without the -overload'servomotor 90, the yconduit 149 may be removed andthe opening `into.which the conduit 140 was .Connected maybe closed as by a plug. Underthese conditions an increase in evaporator pressure reduces uid howAthrough -theiport 212 thereby reducing the pressure I.differentialacross the piston 11,0 permitting the valve 114 to move further awayfromits seat 116. If both the servomotor VS90 and control 290 are used incombination to supply juid to the chamber 1'54, the valve member .114,during periods when the evaporator pressure is such as to causeoverloading of the motor 22, is positioned relative to its vseat'116 -torestrict the inlet pressure of the compressor 11o a value such as toprevent `undesired overloading of the motor 22 as described it beingrealized at'thi's time that the valve 210 will prevent uid flow throughthe port 212 and the conduit 222 is effectively plugged and the valvemember 114 is controlled by the valve 113.6. As the evaporator and/ orcondensing ,pressures are reduced into the `rangewhi'ch will not causeundesired overloading of the motor 22, the valve 134 will plug the port136 and conduit 140 is in effect plugged calling for 'full open positionofthe valve member 114. Asthe evaporator pressure tends to be loweredbelow the desired pressure, the valve member 114 againthrottles fluid'owand is regulated by the control 200. The reduction in pressure in theevaporator is transmitted to the chamber`202 causing the valve`210 toopen the port 2'12 for'uidiowto the chamber 154for movementof the piston110 and valve/114 upwardly whereby uid ow throughthe port 116 is reducedto the vapor withdrawing effect of the compressor 1 on the evaporator10.

"If desired unidirectional fluidow valves 230 may be placed in either-orboth of the conduits 140 and 222 to insure that there is no reverse uidflow therethrough. It will thus be evident that in the form of theinvention disclosed in Figs. 4, '5 and 6, the refrigerating system actsto prevent undesired overloading of the Vmotor 22 and furtherpermitscontinued operation thereof without causing an undesiredlowtemperature of the evaporator I;and.space 12.

1n .the modification shown in Figs. 7 and 8, there is shown a gasolineengine 22a having a4 governor 250 for controlling the speed of operationthereof between predetermined limitsand which also includes `theregulator 12001'for controlling the refrigeration eiect of thevcompressor 1 and the load limiting features as shown .in .Figs 1 and A.Thisgovernor is controlled by atpiston cylinder combination'ZSZ shownconnectedin the system in Fig. 7 and in detail'in Fig. 8 and morecompletely disclosed in my said copending application Serial No. 74,586.In this form the control mechanism 18a is actuated at highcompressor,powerrequirements to control .the valve member'1`14 relative'to .the seat 116 to prevent the 4power requirements of thecompressor'from exceeding the power which-*may safely be deliveredby theengine 22a in a mannersmiiar to that described above under control o'fthe servornotor'-90. The vmechanism 200 upon a reduction inthe-temperature 1of space 12 as reflectedby a reduction in `evaporatortemperature to 'first actuate the governor controlling combination ordevice 252 Ato reduce 'the speed of 'the engine 22a tolower thel pumpingcapacity of 'the compressor '1 to prevent an undesired reduction intemperature ofthe space '12. Since engines, and especially air cooledengines, do not perform well below a-mnirnum speed it is not desirableto continueto reduce the speed below this minimum speed. In manyinstances this minimum -speed results in drivingthe compressor at aspeed in which it reduces the temperature of the evaporator 10lsufficiently to reduce the temperature of the space 12 below thatdesired. Under these conditions the mechanism '200 often reduces'theengine speed to the minimum speed then actuates the mechanism 18a tomove the valve member 114 toward the valve seat 116 to throt- 'tle theiiow of suction vapor from the evaporator tothe compressor. The systemof Fig. 7 therefore provides a continuously operating refrigeratingsystem whichis prevented from overloading the engine by throttling ofthe suction vapor and prevented from reducting the'temperature of thespace 12 below .a desire'dtemperature by reducing the engine speed toreduce the capacity of thc compressor and by throttling the suctionvapor to'the compressor to further reduce the capacity of thecompressor. The combination 252 has a fluid inlet 1254 which isconnected as by means of branch conduit.256 to the conduit 222 wherebyit is under control of the apparatus 200 shown in Fig. 6. The apparatus200 also acts to control the valve 114as described in connection withthe system of Fig. 4. The inlet 254 opens into a chamber 258 closed atits upper end by a piston 260`having a restricted Vfluidow passageway262 therethrough and opening into a chamber 264 above the piston 260.The chamber 264 has an outlet 266 connected by means of conduit 268directly to the inlet of the compressor 1 whereby the chamber 264 ismaintained at all times substantially -at vthe inlet pressure to thecompressor 1. A pistonrod 270 Vof the piston 260 extends .outwardly of.the combination 252 for connection with the governor 250. The chamber254 is suitably sealed against loss of Huid to or reception of fluidvfrom the ambient air 'by means of bellows 272.

`It is believed that it will be apparent from the foregoing that as thevalve 210 is opened to permit a greater uid ow through the port 212, asdescribed above, uid will pass through conduits 222 and 256 to thechamber'258 causing Aa pressure increase in the chamber'258 and amovement of the piston 260 and rod 270 downwardly to move 4the throttletoward closed position to decrease the compressor speed. Movement of thepiston 260 downwardly maybe limited by a cylindrical stop 274 or 4thethrottle movement under control of the piston 260 toward closedrpositionmay be limited by any other suitable means whereby the minimum operatingspeed of the engine 22a maybe predetermined. By such a combination, theengine may be operated continuously within a speed range which permitsof suicient cooling by the fan 276 with which engines of the typecustomarily used for these applications are equipped, prevents theevaporator 10 and space 12 frombeing cooled below the desiredtemperatures, and to utilize the savings in fuel which are present -withreduced speedioperation.

What is claimed and is desired to be secured by United StatesiLetters'Patent is as follows:

1. In a refrigerating system, a compressor having van inlet and anoutlet, an evaporator connected to receive refrigerant from saidcompressor and having anoutlet, a suction vapor passageway connectingsaid evaporator outlet to said compressor inlet, a valve in said suctionpassageway fortcontrolling fluid flow therethrough and a pair vof valveactuators operatively inter-connected to-,said valve to actuate saidvalve toward a closedyposition as a result ofthe interaction oftheetects of said actuators,-a first of said actuators vbeingresponsive toanoperating con-v dition of said evaporator to urge said valve toward avclosed position in response to a rst magnitude of said evaporatorcondition, a second of said pair of actuators being responsive to anoperating condition of said compressor to urge said valve toward aclosed position in response to a first magnitude of said compressorcondition, 4a means for driving said compressor at aV reduced speed, andmeans operatively connecting said first actuator to said driving meansrendering said first actuator effective to control saidV driving meansto reduce the speed at which said compressor is driven in response to asecond magnitude of said evaporator condition. Y i,

`2. In a refrigerating system, a compressor having an inlet andanoutlet, an evaporator connected to receive Vrefrigerantfrom saidcompressor and having an outlet, a suction vapor-.passageway connectingsaid evaporator outlet to said compressor inlet, a valve in said suctionpassageway for controlling fluid flow therethrough and a pair of valveactuators operatively inter-connected to said valve to actuate saidvalve toward a closed position as a result of the interaction of theeffects of said actuators, a first ot said actuators being responsive toan operating condition of said evaporator to urge said valve toward aclosed position in response to a rst magnitude of said evaporatorcondition, a second of said pair of actuators being responsive to anoperating condition of said compressor-to urge said valve toward aclosed position in response to a first magnitude of said compressorcondition, means having a variable power output for driving saidcompressor, and means operatively connecting one of said actuators tosaid variable power means rendering said one actuator effective tocontrol said variable power means in response to a second magnitude ofthe condition to which it is responsive. 3. In a refrigeration system, acompressor, an evaporator, fluid tlow means interconnecting saidcompressor and said evaporator for providing a regulated tlow of tluidfrom said compressor to said evaporator, a fluid ilow meansinterconnecting said compressor and said evaporator for providing a uidllow path from said evaporator to said compressor, means including aflow-restricting device in said last-named fluid flow means, afluid-powered operating means for said device, and a speed control meansfor regulating the rate at which said compressor operates, a pair ofactuators for supplying actuating uid to said fluid-powdered operatingmeans and said speed control,

means rendering the operation of a rst of said actuators responsive toan increase in the work done by said compressor causing it to supplyoperating fluid to said uidpowered operating means to cause saidnow-restricting device to reduce the rate of removal of fluid from saidevaporator, means rendering a second of said actuators responsive to adecrease in pressure in said evaporator causing said actuator to supplyiluid to said speed control means causing the latter to reduce the speedof said compressor and to said huid-powered operating means to causesaid flow-restricting device to reduce the ilow of fluid from saidevaporator to said compressor, and means rendering said speed controlmeans inefective to reduce the speed of said compressor below apredetermined minimum.

4. In a refrigerating system, a compressor having an inlet and anoutlet, an evaporator having an inlet and an outlet, a first fluid flowpassageway interconnecting said compressor outlet and said evaporatorinlet and providing a regulated flow of fluid from said compressor tosaid evaporator, a second fluid ow passageway interconnecting saidcompressor inlet and said evaporator outlet for providing a fluid ilowpath from said evaporator to said compressor, a third flow uidpassageway communicatively connecting said compressor outlet and inletin by-pass relation to said evaporator and including means restrictingiluid flow therethrough, a first flow controlling element in said thirdpassageway intermediate said third passageway restricting means and saidcompressor outlet and controlling fluid flow therethrough, a second lowcontrolling element controlling fluid flow through said secondpassageway, a pressure sensitive element connected to respond to thepressure in said third passageway intermediate its said restrictingmeansand` said first ow controlling element and, having a pressureresponsive .portion opera- Vtively connected to said second ilow elementfor actuation thereof, a'par of pressure sensitive elements operativelyconnected for actuation of said first ow controllingv element andoperable upon increase in pressure -to actuate said first flowelementvto open position, one of said actuators being responsive to thepressure of the fluid in said compressor outlet, and the other of saidactuators being responsive to the pressure of the fluid inlsaidcompressor inlet.

S. In a refrigerating system, a compressor having an'inlet and an'outlet, an evaporator having an inlet and an outlet, a `firstiluid flowpassageway interconnecting said com,- pres'sor outlet and Vsaidevaporator inlet and providing a regulated flow of fluid from saidcompressor to said evaporator, a second tluid flow passagewayinterconnecting said compressor inlet and said evaporator outlet forproviding a fluid flow path from said evaporator to said compressor, athird fluid flow passageway communicatively connecting said compressoroutlet and inlet in by-pass relation to said evaporator and includingmeans restricting uid ow therethrough, a first flow controlling elementin said third passageway intermediate said third passageway restrictingmeans and said compressor outlet and controlling fluid How therethrough,a second flow controlling element in said passageway in lby-passrelation to said first element and controlling fiuid flow through saidthird passageway, a pressure sensitive element connected to respond tothe pressure in said third passageway intermediate its said restrictingmeans and said flow controlling elements and having a pressureresponsive portion, means regulating the rate at which said compressoris operable to remove refrigerant from said evaporator and operativelyconnected to said pressure responsive portion for actuation thereby, apair of sensitive actuating elements operatively connected to said ilowcontrolling elements for control thereof, means rendering one of saidactuators responsive to an operating condition of said compressor, andmeans rendering the other of said actuators responsive to an operatingcondition of said evaporator.

6. In a refrigerating system, a compressor, an evaporator, a liquidrefrigerant passageway including a liquid flow controlling meansinterconnecting said compressor with said evaporator for supplying aregulated flow of liquid refrigerant to said evaporator, a suctionrefrigerant passageway including a suction iluid flow regulatorinterconnecting said evaporator with said compressor for supplying aregulated ilow of suction refrigerant to said compressor, afluid-powered operating means for said suction fluid flow regulator, atrst actuating device responsive to a minimum operating condition ofsaid evaporator and having a controlling element operatively connectedto said fluid-powered operating means to supply operating iluid to thelatter causing it to operate said suction tlow regulator to reduce theflow of refrigerant to said compressor, a second actuating deviceresponsive to maximum operating conditions of said compressor and havinga single controlling element adapted to supply operating fluid to saidfluid-powered operating means to cause the latter to reduce the rate ofow of suction refrigerant to said compressor, said last-named singlecontrolling element having two pressure sensitive elements each having apressure responsive portion, fluid flow means operatively connectingsaid last-named single control element with said fluid-powered operatingmeans, pressure conveying means connecting one of said pressuresensitive elements to respond to the intake pressure of said compressor,and pressure conveying means connecting the other of said pressuresensitive elements to respond to the outlet pressure of said compressor.

7. In a refrigerating system, a compressor, an evaporator, a liquidrefrigerant passageway interconnecting said compressor and saidevaporator for providing a regulated flow of liquid refrigerant fromsaid compressor to affamati saidevaporator, 'a'suction 'conduit'interconnecting said 'coinpres'sor and saidevaporator'for providingVafinid'flow path *from sa'id evaporator to 'saidconipressoig a valveregulating' the flow of suction refrigerant through said suction'conduit to'regulate'the rate 'at which suction krefrigerant' :is'removed "from said 'evaporator' by said .compressor-independently of`the -Vrate at lwh'i'c'h liquid 4refrigetant 'is' supplied to saidevaporator 'by said liquid flow regulating -means, atrst'actuatoroperatively connected Ato control said valve,'means'rendering-said firstactuator responsive to an increase in the work done `by saidCompressorgtomove 4said-valveV toward closedrpositiOn to reduce 'the'suction refrigerantadmitted to said compressor, means controllingthesp'eed at which saidf compressor 'is driven, a lscond'actuatorresponsive to an operating condition ofsaid'evaporator, fandr'neans'vrepnderingsaid second actuatojr 'responsive to a decrease-inthe magnitude of said evaporator condition'to actuate said compressorspeed controlling means to reduce' the speed at which saidcornpressor'isdriven.

References 'cited in 'thefueiof' this ypatent Jones Nov.`- 14,' l1933Thomas "July'24, '1934 Smith Nom-24, T1936 McCormack MayL1'1,`-1937Euwer Sept. 30;19'41 Homes Dec. 15,11942 Henny "June'l, '-11943 WinklerYlune 27, 1944 Newton lauf-I6, 1945 'Atchison 'Nov.-`23,11948 I Zearfoss:Sept 20, "1949 Lathrop I-Feb.`= 14, 1950 Lange lun'e, T1950 Schulze etval. Sept."2'6,"1950 Jones -`Jan. 8,' L1952

